Distribution Rule of Multiphase Corrosion Flow and Prediction of Dew Point Top Corrosion Characteristics in Return Flow System of Atmospheric Pressure Tower Top

Aiming at the return flow system of atmospheric pressure tower top in a refining and chemical enterprise, a multi-component fluid phase-ion equilibrium model was constructed by Aspen Plus software. The gas-liquid equilibrium distribution of corrosive media HCl and H₂S in the tower top volatile pipeline was obtained, and the quantitative characteristics of corrosion flow distribution in the tower top pipeline were predicted. The results show that the mole flow rates of HCl and H₂S in the aqueous phase increased significantly with the decrease of temperature. The dew point temperature was determined to be 101.2 ℃ by the initial dissolution temperature, and the lowest pH at the dew point could reach 2.59. The dew point corrosion occurred near the outlet pipeline of the tower top. There were three areas with high liquid film coverage in the tower top outlet pipeline, which were the vertical pipe wall of volatile pipeline inlet, the inner wall of the elbow and the lower wall of the horizontal pipe. At the dew point, most of the HCl gas dissolved in the initial liquid film formed by the condensate, so the area where the initial liquid film converges was the area where corrosion occurred frequently.